As an information recording element that expresses non-volatile memory property, ferroelectric memory elements using a ferroelectric layer are known. Recently, use of an organic material for the ferroelectric layer thereof has been considered. This is because a thin film of a ferroelectric substance can be formed by applying or printing a solution of an organic material to utilize the solvent solubility thereof, and the film can be utilized as a ferroelectric layer. In view of such characteristics, application of the film to mass-pervasive type information recording apparatuses is expected. For example, it is application to recording elements such as tag, specifically RFID (Radio Frequency Identification) tag, ID tag, IC tag, RF (Radio Frequency) tag, wireless tag, electron tag and the like, and the like.
It is well known that fluorine group polymers such as polyvinylidene fluoride (PVDF), vinylidene fluoride-trifluoroethylene copolymer (P(VDF/TrFE)) and the like show ferroelectricity. However, since fluorine group polymers do not show good film forming property, which causes problems in terms of the uniformity of film thickness, smoothness of film surface and the like.
On the other hand, patent document 1 describes that poly α-amino acid with helix geometry shows ferroelectricity and patent document 2 proposes a ferroelectric memory element having a ferroelectric layer formed from poly α-amino acid. In addition, patent document 3 proposes a ferroelectric memory element having a ferroelectric layer formed from a mixture of poly α-amino acid and a different polymer (specifically, polymethylmethacrylate (PMMA) etc.).
However, a ferroelectric memory element utilizing the poly α-amino acid specifically described in patent documents 2 and 3 has a problem of decrease in the memory property at high temperature, and cannot be dissolved in a particular solvent. Therefore, the element cannot be used as a material that can be printed on and is requested to be dissolved in various solvents. Since a technical approach for resolving such problem has not been taken, practicalization has not been made as yet.
On the other hand, patent document 4 describes a method including applying an electric field to poly α-amino acid at a temperature not less than the liquid crystal transition, and using same for an optical memory. However, patent document 4 only discloses that an optical memory capable of changing the reading wavelength can be provided by applying an electric field, and does not at all mention that it can be used for a ferroelectric memory element which is based on a completely different principle, or the memory property of a ferroelectric memory element at high temperature.